A pattern fill operation employs a pattern in a repeating structure to fill a graphics object such as a polygon. In a page description languages like PostScript, patterns are typically reduced to images at the device resolution and stored in a pattern cache for later use to render objects in device space. However, storing the image for a large pattern in the pattern cache at high resolutions takes huge amounts of memory. This requirement of large amounts of memory is disadvantageous.
PostScript printers have traditionally either aborted a printed page upon exceeding the pattern cache capacity or have reverted to some method that was either slow, poor in quality or both. The interaction between the interpreter and the rendering made it difficult to band the display list and execute in a page pipeline mode where different pages are, simultaneously, in different stages of the conversion from page description language to page bit map. The PostScript Red Book, a reference for use of PostScript, explicitly limits the PostScript Language primitives that can be used to describe a large pattern. This limitation is an attempt to avoid the problems of caching large pattern primitives.